In the assembly of a unitized body, the first step in the assembly or the framing of the body brings together at the first framing station on the body assembly production line various major panels, locates the panels in assembled relationship with each other and, while the panels are so located, robotic welders weld the panels to each other to form a vehicle body shell. Typically, the first step in the framing process will involve a vehicle body floor panel, right and left-hand side panels, a fire wall panel and a roof panel or roof header members extending transversely between the upper portions of the body side panels. Once the panels are assembled to each other at the first framing station, access to a portion of the individual panels at the interior of the body shell becomes restricted, and it is thus conventional practice to perform several preassembly steps on the individual panels before they are advanced to the framing station. In the case of a body side panel, for example, the panel is initially stamped from sheet metal, and is then advanced through a series of work stations where additional parts, such as door latch and hinge reinforcements, mounting brackets, stiffeners, etc., are welded in place on the sheet metal stamping.
Prior known devices include a conveyor for conveying a body side panel to a series of work stations where the pre-framing operations referred to above are performed on the body side panel. The conveying system includes a carrier mounted for movement along an elevated horizontal path extending past a series of work stations. A generally rectangular open support frame is mounted along one edge upon the carrier for pivotal movement relative to the carrier about a horizontal axis parallel to the conveying path. While the carrier is being advanced from one work station to the next, the support frame is maintained in a horizontal elevated position well clear of the plant floor. The body side panel, during this transfer step, is held against the underside of the support frame by what will be referred to generally as a plurality of clamps. Upon arrival at a work station, the carrier is stopped and a manipulator associated with the conveyor pivots the support frame downwardly to a vertically inclined or vertical position relative to the carrier to locate the body side panel in an adjacent relationship with a stationary panel receiving work frame at the work station. The panel is transferred from the stationary work frame and the support frame is then pivoted back upwardly to its horizontal position clear of the panel on the work frame. After the work operations have been performed on the panel while the panel is held on the stationary work frame, the support frame is again pivoted downwardly, the panel is reclamped to the support frame, and the support frame with the panel is then pivoted back upwardly to its horizontal position relative to the carrier for advancement to the next work station.
Most, if not all, of these work stations are automated, and automated assembly of this type requires a precise positioning of the panel relative to the automated equipment so that the various parts are precisely located on the panel. Achievement of such alignment and access to the desired locations on the panel by the assembly tooling cannot always be achieved while the panel is supported on the conveyor, and at the typical work station, a stationary work frame especially designed to support the panel in alignment with the tooling is employed to support the panel while the particular assembly of operation is performed. This in turn involves a transfer of the panel from the conveyor to the work frame to perform the assembly operation and the subsequent transfer of the panel back from the work frame to the conveyor after the operation is completed.
To accomplish such a transfer, a transfer device must be accurately aligned both with the conveyor and with the work frame upon which the body panel was positioned in alignment with the automated tooling. In that the typical conveyor will extend for 100 feet or more and includes several work stations, precise alignment of all portions of the conveying path with a fixed reference point is difficult to achieve in practice. Insofar as the path of movement of parts or panels along the conveyor is concerned, precise positioning is of little concern during transit of the panels between successive work stations. However, at arrival at a work station, the panel must be precisely positioned relative to the transfer mechanism which in turn must be precisely positioned relative to the work frame.
Once the major panel is precisely positioned relative to the stationary work frame, the part to be assembled to the body panel must be loaded and transferred to a precise position with respect to the body panel for subsequent assembly operations, such as welding. The present invention is directed to such a part loading device for transferring parts from a first position generally disposed in a first plane to a second position generally disposed in a second plane precisely positioned relative to the body panel and the stationary work frame. The part is taken from a conveying path, or is manually loaded, for loading and transfer by the present invention to assure proper placement of the part on the stationary work frame within the desired degree of precision. The present invention providing soft touch operation as the present invention reaches the end limit of travel in either direction.